Coelogyne is a genus of over 200 sympodialepiphytes from the family Orchidaceae, distributed across India, China, Indonesia and the Fiji islands, with the main centers in Borneo, Sumatra and the Himalayas. They can be found from tropical lowland forests to montane rainforests. A few species grow as terrestrials or even as lithophytes in open, humid habitats. The genera BolborchisLindl., HologynePfitzer and PtychogynePfitzer are generally included here. The genus is abbreviated Coel in trade journals.

The wide distribution of this genus has resulted in a wide variety of temperature requirements from species to species, some requiring cool to cold conditions to grow and bloom reliably, while others need decidedly warmer temperatures to achieve the same.

The scientific name is derived from the Greek words koilos (hollow) and gyne (woman), referring to the concave stigma.

This genus lacks the saccate base of the labellum, a typical characteristic which is present in the other genera in the subtribe Coelogyninae. The free lip has high lateral lobes along the basal part of the labellum (hypochile) and smooth, toothed or warty keels.

Inflorescences often show a small to very large number of showy, medium-sized to large flowers. They may arise either from the apex of the newly completed pseudobulb at the end of the growing season (as in Coelogyne fimbriata), or may precede the new growth in early spring (as in Coelogyne cristata). The typical colour range of this genus is white, through tawny brown to green, and occasionally peachy tones. All species have four pollinia.

They have often a sweet scent, attracting different kinds of pollinators, such as bees, wasps and beetles.

A few species are commonly known as 'necklace orchids', because of their long, pendant, multi-flowered inflorescence.

The cooler growing species such as Coelogyne fimbriata, Coelogyne ovalis, Colegyne fuliginosa, Coelogyne cristata, Coelogyne flaccida, Coelogyne nitida originate in the Himalayan region of India and southeast Asia. They require a decided rest period during winter during which they receive no feed, very little water (enough to prevent pseudobulbs shrivelling), cool to cold temperatures and high light. These conditions seem to aid flowering in spring for some growers, though others report that more constant conditions can also produce regular flowering.

Coelogyne 'South Carolina' (C. pandurata × C. burfordiense), sometimes called "the black orchid" because of the black coloration of the heavily patterned and structured lip.

The traditional taxonomy of the genus Coelogyne is still disputed. Coelogyne has been subdivided in 23 sections or subgenera by De Vogel (1994) and Clayton. Molecular data show that Coelogyne is paraphyletic and should be reorganised. It should include the genera Neogyna and Pholidota, and several sections should be removed, including Cyathogyne, Tomentosae, Rigidiformes, Veitchiae and Verrucosae. This new genus Coelogyne should then contain about 160 species.[1]